Many substances exist which are toxic in large doses, but have beneficial effects in smaller doses. For example, when administered at the correct dosage level, chemodenervating agents (e.g. botulinum toxin, tetanus toxin, etc.) can be useful in the treatment of hyperhidrosis, muscular spasm and/or contracture, facial and other wrinkles, headache, etc.
One approach to determining correct dosage levels involves assaying the in vivo activity of chemodenervating agents. U.S. Pat. No. 5,401,243 describes methods for assaying the in vivo activity of injected botulinum toxin. However, no methods have been described for assaying the in vivo activity of topically-administered botulinum toxin. In fact, until very recently, no formulations for topical administration of botulinum toxin have been described. Such topical formulations were recently described in co-pending U.S. patent application Ser. No. 11/607,436, entitled “BOTULINUM NANOEMULSIONS,” filed Dec. 1, 2006.
Therefore, there is a need for the development of methods of determining correct dosage levels for topical administration of chemodenervating agents (e.g. botulinum toxin). There is a need for the development of methods of measuring the activity of topically-administered chemodenervating agents in vivo.